Which term refers to authoritarian rule by a single individual?

The term that refers to authoritarian rule by a single individual is dictatorship. In a dictatorship, a single leader holds concentrated power and often maintains authority through oppressive means, limiting political pluralism and civil liberties. This concentration of power can lead to governance that disregards democratic processes and may involve force or coercion to suppress dissent.

Monarchy, while it also includes strong centralized power, typically refers to hereditary rule where a king or queen may govern, and the power structure can vary greatly; some monarchies may have democratic elements. Oligarchy involves power held by a small group of people, which is distinct from the rule of a single individual. Theocracy is a system of governance in which religious leaders control political power, which again differs from the concept of an individual holding authoritarian rule.